1. Field of the Invention
The present invention relates to a magnetic recording medium which is excellent in high density recording/reproducing characteristics and a method for producing the same.
2. Description of the Related Art
These days, the recording density of a magnetic recording/reproducing equipment has been increased, while its size has been reduced. As one of the magnetic recording media which can exceed the limit of recording density performance of a conventional coating type magnetic recording medium, a thin film magnetic recording medium attracts attention. A thin film type magnetic recording medium having a magnetic layer comprising Co, Ni and O is commercially produced and sold as a magnetic tape for VCR (Video Cassette Receiver). To produce the thin film magnetic recording medium with good productivity, for example, a magnetic layer is continuously vapor deposited on a tape-shaped polymer substrate which is transferred along a circumference of a cylindrical can in a vapor deposition apparatus. In such method, when the magnetic layer is obliquely deposited, the high density recording/reproducing characteristics are improved because of the contribution of a magnetization component in a direction vertical to a plane of the magnetic layer, in comparison with the conventional coating type magnetic recording media.
The thin film magnetic recording media produced by the above method have contributed greatly to the popularization of a home-use camcorder type VCR, and are expected to be used in a next generation home-use compact digital VCR, in particular, a digital VCR which is compatible to high definition TV.
One of the important factors in realizing a home-use compact digital VCR which makes long time recording possible is that a cassette tape should be made small while its recording capacity should be increased. That is, while the cassette tape is required to be miniaturized for conveniently carrying and using it, it is required to have a large recording capacity which can record a large amount of digital signals which accommodate a long time recording. To satisfy both requirements, it is essential to increase the recording density of the signals on the magnetic tape. However, the currently used thin film magnetic tapes do not necessarily have the high density recording performance which satisfies the above requirements.
The current home-use VCR uses a tape traveling system comprising a rotating cylinder which carries a magnetic head. As one of the measures for further miniaturizing the magnetic recording apparatus with such system, it is contemplated that, by the introduction of an overwriting system, an erasing head is eliminated to reduce the size of the rotating cylinder. To introduce the overwriting system, the magnetic tape should have excellent overwriting properties, which depend also on the properties of the recording head. However, the current thin metal magnetic tape does not have the overwriting properties which can accommodate with the introduction of the overwriting system, when it is used in combination with a generally used ring-type magnetic head having a saturation magnetic flux density of about 1 T or less and a gap length of about 0.2 to 0.3 .mu.m. In particular, when a high frequency signal having a wavelength of 1 .mu.m or less is overwritten on a pilot signal having a wavelength of 10 .mu.m or longer which is used for tracking, a residual level of the pilot signal is very high, and such high residual level of the signal prevents the practical use of the magnetic tape in the overwriting system.
In view of the above drawbacks of the currently used thin film magnetic tapes, it is highly desired to provide a high quality magnetic tape having a higher recording density performance and better overwriting properties to realize a home-use compact digital VCR.